Chemical of the Week 15 – Urea


So again this week in the news it’s chemicals that are getting big industry into trouble. This time the culprits are the car exhaust gases carbon dioxide and nitrogen dioxide. But behind the scenes it’s the chemical urea that has caused the problem. Cars need fuel, and using any hydrocarbon based fuel such as petrol or diesel will produce carbon dioxide. The nitrogen oxides are produced by the high temperature combustion of nitrogen gas present in air. Diesel engines are notoriously more ‘dirty’ than their petrol counterparts but of course everyone knows they give more miles to the gallon. The problem that faced car manufacturers was that consumers wanted diesel transport at accessible prices but the manufacturers needed to meet the environmental legislation with regards to emissions.

So the chemists came up with some clever design of the emission chamber, using selective chemical reduction (remember we want the nitrogen oxides to be converted to nitrogen which is a chemical reduction ) that was aimed at reducing nitrogen oxide emissions by 90%. This system uses ammonia or an associated compound such as urea as the reductant. Urea has the formula CO(NH₂)₂. The molecule has two —NH₂ groups joined by a carbonyl (C=O) functional group. It’s IUPAC name is amino methanamide and is also known as carbamide. It is more commonly known as a biological molecule as it is produced in the body by the breakdown of proteins. It has a neutral pH so it’s safer for the body than ammonia which would raise pH levels to dangerous levels. The kidneys then transfer urea from the blood to urine in order to allow it to be expelled from the body. It can also be made synthetically from ammonia and carbon dioxide and its main industrial use is in fertilisers.

Using urea is were the problems for Volkswagen started to occur. In large vehicles storage of a tank of urea was no problem but in smaller cars such as the Jetta, it was just not viable. So they turned to another technology LNT ( lean NOX trap) to store the NOX emissions. The problem with this technology is it could not reduce the emissions to the levels required by increasingly stringent environmental legislation and that’s when the idea of allegedly using software that circumvents emissions testing for nitrogen oxide gases. So how did Volkswagen finally get caught – it looks like the directors of a European agency, the International Council on Clean Transportation, became suspicious when comparing the emissions of European cars with American cars. They were working with West Virginia University’s Centre for Alternative Fuels Engines and Emissions to see why the European industry could not produce cars for sale in Europe with as clean emissions as those they sold in the US. Now it looks like 11 million cars have been caught up in this scandal and there is talk of $18 billion of fines – and reports now say there is to be a criminal investigation for fraud. The funny thing about all of this, it seems that the other car manufacturers must be peeing their pants laughing as it turns out they may escape blame as they stuck to injecting urine into their convertors !

Chemical of the Week 14 – Tyrian Purple

This post was inspired by staff room chat a couple of weeks ago. Bemoaning the end of summer our attention turned to the lovely colours some of the female staff where wearing. The bright colours brought me back to A level Latin class and our translation of The Aeneid. You see, this topic of conversation is not a new one as even back about 30BC Virgil waxed lyrical about the Tyrian purple cloak that Dido had made for Aeneas heading into battle, he even remained cloaked in it on his funeral pyre !  It was also the colour of choice for the Roman ruling classes.  The status of the individual was reflected in the width of the purple stripe on their toga with the Emperor having a ceremonial toga of Tyrian purple.

Natural dyes are derived from plants, invertebrates, or minerals. The majority of natural dyes are vegetable dyes from plant sources and other organic sources such as fungi and lichens. Tyrian purple has been around since approximately 1600BC and is obtained from the hypobranchial gland of various species of marine molluscs. It was original extracted and marketed as a dye in the city of Tyre, now the fourth largest city in Lebanon but back in the ancient world a major commercial centre. It took 12,000 molluscs to produce approximately 1 1/2 grams of this dye so it was considered as valuable as silver. The molluscs were crushed and boiled up to release the colourful chemical required for dying. The chemical, 6,6-dibromoindigo, that is responsible for Tyrian Purple was identified at the turn of the last century by the chemist Paul Friedlander.  He was able to isolate 1g of the dye from the molluscs and analyse it to obtain an empirical formula ( using the structure below can you work it out !)   The presence of bromine in the molecule was unexpected and it is believed that it is what causes the reddish tinge to an indigo based molecule.


The background to the production of synthetic dyes is interesting as it took off when dyes started to be synthesised from coal tar. Coal tar contains various aromatic hydrocarbons like toluene, xylene, benzene and is obtained from the distillation of bituminous coal. Most organic compounds are colourless but certain organic molecules with an extensively delocalised electron system will absorb in the visible range of the spectrum. Synthetic dyes have the advantage of being less costly and more reliable to produce. The famous chemist William Perkin made the first synthetic dye Maurvin in 1856. His legacy includes the Perkin Medal which is widely acknowledged as the highest honour in American industrial chemistry and also the RSC journal Perkin Transactions (1997-2002). By the end of the 1800s indigo and alizarin had also been made synthetically and so began our colourful journey. Today there are over 3600 different types of synthetic dye and 500,000 tonnes are produced each year. Chemists now tailor the molecules so that they do not present any environmental problems and that they adsorb on to the desired substrate eg cotton, polyester. Environmentally the high water to dye ratio in the dying process has resulted in major pollution problems with waterless dyeing being the holy grail in the textiles industry. We’ve come a long way from the marine molluscs but interestingly natural dyes are all the rage again ! Batik scarf anyone ?

Chemical of the Week 13 – Parabens

imageThere is a lot of cosmetic marketing based around the tag line ‘ no chemicals ‘ but of course what they really mean is ‘no parabens’. So the big question is what is a paraben ? Parabens are a family of compounds based around esters made from 4-hydroxybenxoic acid. The most common being used are methylparaben, ethylparaben, n-propylparaben, n-butylparaben and isobutylparaben. The ‘para’ in the name comes from the 4 position of the hydroxy group in relationship to the acid group which is referred to as para ( two is ortho, three is meta ). These compounds are nowadays obtained by industrial synthesis, however they can be found in plants such as blueberries or in grapefruit where they act as antimicrobial agents. They are made synthetically by the esterification of para-hydroxybenzoic acid with a corresponding alcohol such as methanol – this can be linked to the A2 course through both the esters and organic synthesis topics.

Parabens are used because they are very good preservatives and prevent the degradation of the cosmetics. They are found in most common cosmetics including face creams, toothpaste, shaving foams and under arm deodorants. There have been some reports on the safety of parabens, in particular in under arm deodorants, as they have been linked to breast cancer. The worry over their safety has been in the public domain since a scientific report in 2004 which reported parabens being present in the breast tissue of cancer patients. The paraben molecule has some similarity to oestrogen and the worry is that they can latch on to hormone receptor sites in the body. This may cause the increase in the expression of oestrogen response genes in human cells and could lead to increasing breast cell division and the growth of tumors.

Legally the European Union have acted and regulations limiting concentrations of butylparaben and propylparaben in cosmetics products have taken effect from April 2015. The new requirements set a maximum concentration of 0.14 percent for the two in addition to banning their use in certain infant creams. This legislation illustrates the problems that the chemical industry face – is it being driven by hard science or by public opinion ? Looks like in the meantime it’s the cosmetics and toiletries companies who are winning as they sell us ‘paraben free’ goods which tend to be more costly.  And by the way ‘chemical free’ there’s a world I’d like to live in – oh but that would be a vacuum then !

Some More Periodic Tables !

This is an easy post this week as it’s a round up of some more Periodic Tables I’ve spotted since my last post on them.  First of all thanks to Professor Ken Seddon for forwarding me this picture of a periodic table he found displayed in the faculty of chemical sciences in Madrid.


Add to that this fantastic Periodic Table currently on display at the Ulster Museum in Belfast for the Elements display  -again showing elements where possible.


I’d encourage everyone to take a trip to this exhibition.  It’s a brilliant example of how thoughtful design and informative displays can make Chemistry so engaging and accessible to the general public.  Whilst walking around I heard one teenager asking her friend what the most dangerous element was, the friend answering ‘fire’ and the friend replying back ‘doh – that’s not an element ‘ and I thought there’s hope for us chemistry teachers yet! By the way answers on a postcard!

Anyway next up one that fits in very well with AS course as we are just about to cover emission spectra.


Now for a great resource from the University of Nottingham.  The QR codes link to the Periodic Videos for each element.  I’ve used this as an introduction to the Periodic Table topic for KS3 using iPads ( you just have to download a QR reader).


Here’s another one that I like as it clearly shows the more abundant elements.


There is  great clip on the Periodic Videos website where they take a trip to the Science Gallery in Dublin and one of the chemists weighs himself and the machine prints out the % abundance of each element in his body.  Looks like we have more in common with supermodels than we thought ! Here’s a link to the clip below.

Finally, it seems that everyone is getting in on the Periodic Table act and there are some very strange things out there.  I’ll leave you with this one, really don’t see the link myself !


Chemical of the Week 12 – Sulfuric Acid


Sulfuric acid is referred to as the king of chemicals. It’s one of the first acids we meet in chemistry class.  156 Million tons are produced world wide annually and it is considered a barometer of industrial activity. It was called “oil of vitriol” by medieval European alchemists because it was prepared by roasting “green vitriol” -iron (II) sulfate. Today the industrial manufacture of sulfuric acid is by the Contact process, which is studied at GCSE ( unfortunately a list of  equations to memorise with a wee bit of Le Chatelier thrown in !) We use sulfuric acid in just about everything including batteries, paint, fertilizer, ore processing, paper processing, steel production and water treatment. Oh and don’t forget a more macabre use. The Mafia are quite fond of getting rid of corpses in vats of concentrated acid, but it seems this may just be the stuff of legend. Recent research suggest that the disappearance of a body in couple of minutes as reported by the Mafia informants just does not happen when scientists set up trials with pig carcasses.

Pure sulfuric acid is a colourless, odourless, oily liquid. It freezes at 10.5°C. When dilute it displays typical acid reactions but when concentrated it can act as a catalyst, an oxidising agent and a dehydrating agent- everyone loves the video clip of the dehydration of sugar. Concentrated sulfuric acid is 98% by weight as when it is distilled from an aqueous solution it forms an azeotrope (constant boiling mixture). An azeotrope is a mixture of two or more chemicals ( in this case sulfuric acid and water ) that cannot be separated by basic distillation processes because they share a common boiling point and vaporisation point. When diluting concentrated acid always remember acid to water – I do love a mnemonic “Always do things as you oughta, add the acid to the water, if you think your life’s too placid, add the water to the acid’


But why pick sulfuric acid this week ? Some fantastic photos have been taken recently on the Indonesian island of Java showing amazing jets of sulfuric acid being released from a volcano. Ijen is one of Indonesia’s most famous volcanoes and is of economic importance as it provides sulfur. Described as one of the worlds most dangerous jobs, miners access the crater in the middle of the volcano to access the deposits. Within the crater is a lake called Kawah Ijen that contains 600,000 tonnes of hydrogen chloride, 550,000 tonnes of sulfuric acid, 200,000 tonnes of aluminium sulphate and 170,000 tonnes of iron sulphate. Check out this website with some fantastic pictures of the lake.

Read, Watched, Heard – Part 1

I’ve spotted on lifestyle blogs, some bloggers do a round up on what they’ve read, watched, heard and wore ( now as chemists we can safely leave the last one out !). So I thought this might be a good structure every couple of weeks to list bits and pieces that I’ve been filing away. Then it’s up to you if you find the topic interesting and want to do a bit more delving. So starting this week what I’ve…..
I have put an advance order in for the fantastic Compound Interest book – ‘Why Does Asparagus Make Your Wee Smell’ due out at the beginning of October. Compound Interest has produced some amazing graphics over the last couple of years. Included in my favourites are the 12 molecules of Christmas and the chemicals of the swimming pool.


On Twitter this week I found a link to a fantastic clip by the scientist Ainissa Ramirez, a passionate science communicator. She was an Associate Professor of Mechanical Engineering & Materials Science at Yale University and has recently been named by Technology Review Magazine as one of the world’s 100 Top Young Innovators for her contributions to transforming technology. The clip was on making ice cream and both her presentation and the content are fantastic. I’m going to look out for some more of her material to use in class. Check Ainissa out below !

‘The lack of science skills can hamper adults development’ according to Dame Athene Donald, president of the British Science Association. She says ‘forcing pupils to make subject choices from the age of 14, effectively divides the nation “into sheep and goats, science people and arts people” ‘ I think as science teachers we can all relate to that, totally losing touch with some pupils post KS3. Check out the full article on the BBC site below

Oh, and sadly Oliver Sachs, mentioned in one of my earlier posts, passed away on August 30th.


Chemical of the Week 11 – Meitnerium

imageSo back to the Periodic Table for this weeks chemical of the week. It’s a transuranic element with an atomic number 109. Meitnerium will not be found naturally but is produced artificially by bombarding atoms of bismuth-209 (209Bi) with ions of iron-58 (58Fe) using a linear accelerator. As it is difficult to make and its most stable isotope has a half life of eight seconds so it is probably not the most useful element around. Mietnerium was discovered in 1982 and named after the nuclear scientist Lise Mietner and I think her story is worthy of a blog post as Mietnerium is the only element named after a woman.

Lise Mietner was born in Austria in 1878 of Jewish extraction. She was only the second woman in Austria to obtain a PhD and by the 1912 she was working in the Kasier Wilhiem institute with the scientist Otto Hann. Now this is where it starts to get interesting as together they set about trying to make elements heavier than uranium and by 1917 they had discovered protactinium. During World War One Lise worked at the front as an x ray technician and subsequently returned to the Kaiser Wilhiem institute the under the directorship of Otto Hahn to continue her studies.

In 1938, due to the rise of the Nazis in Germany, Lise had to flee to Stockholm. It was here that she met up with her nephew Otto Frisch and discussed some of the perplexing results that Otto Hahn had been obtaining. Hahn had been bombarding uranium with neutrons and he found barium in the products. It was Meitner who suggested to her nephew that the uranium may be splitting up and the idea of nuclear fission was born. Frisch then passed this information on to Neils Bohr and he reported it in America to great interest. Hahn meanwhile published a paper about nuclear fission omitting Lise’s contribution. By 1944 Otto Hahn had received a Nobel prize for his work on nuclear fission, with no mention of Lise Meitner.

Lise Mietner should be an inspiration to all scientists. She moved in scientific circles that we can only dream of with contemporaries such as Max Planck, Otto Hahn and Niels Bohr to name a few. Einstein even called her ‘our Marie Curie’. She was devastated by the idea that her scientific discovery had been used in the making of the atomic bomb and refused to work on the Manhattan project. She did not let her snub by the Nobel committee stand in her way, but worked on in Stockholm on her research until she was in her 80s. So the fact that she has an element named after her is a fitting tribute, as her legacy will be on the wall of every chemistry classroom and lab forever !